Superimposed multiple cavity mold



2 1953 E. VAN RIPER ET AL 2,663,905

SUPERIMPOSED MULTIPLE CAVITY' MOLD Filed Sept. 6, 1951 i f a z 2 Sheets-Sheet l ATTORNEY Dec. 29, 1 E. VAN RIPER ET AL SUPERIMPOSED MULTIPLE CAVITY MOLD 2 Sheets-Sheet 2 Filed Sept. 6, 1951 which:

around openings in pieces ported on a base Patented Dec. 29, 1953 SUPERIMPOSED MULTIPLE CAVITY MOLD.

Elmer Van Riper, Rochelle-Park, and George W. Frey, Wyckofl, N. J assignors to. United States Rubber Company, tion of New Jersey New York, N. Y., a corpora- Application September 6, 1951, Serial No. 245,286

4 Claims.

This invention relates to an improved method andapparatus' for molding rings of plastic material, or plastic grommets, such as eyelets around openings'in sheet material, particularly textile fabric.

Heretofore, plastic rings and grommets have been molded in cavities formed between mold plates where the heat required to cure or set the plastic was conducted by the mold plates from the outer'periphery thereof to the cavities therein. This required an exterior heating packet to be placed around the mold if the heat treatment was to be applied in a vulcanizing press, or the clamped together mold parts were'placed' in a heated autoclave. amount of labor and apparatus was required to heatand handle the molds.

In accordancewith the present invention the molding and heat curing apparatus is simplified by the elimination molds and a more the heat to the mold cavities. The increase in the heating eiiiciency is particularly noticeable in the grommet curing operation.

The. above and other objects and advantages of this invention will be further described in reference to the accompanying drawings, in

Y Fig. 1 is a cross sectional view of a molding apparatus embodying this invention, and illustrating the method of molding grommets, oreyelets ofsheet fabric;

i Fig; 2 isan isometric view of a raw or uncured plasticring,v one of which isto be placed on each side'ofth'e fabric and around the opening there- 'il'ltoibe molded into a unitary grommet;

Fig: 3 is an-isometric view' of Fig. 4 is a plan view of a plastic grommet molded around an opening in a piece of sheet fabric, in which a part of the grommet is broken .aw'ay to illustrate its construction.

The method and apparatus embodying this in tion with the molding of'grommets around openings in sheet material, such as textile fabrics, but it will be understood that when the fabriois omitted, individual plastic rings may be molded in this apparatus. As'shownJin F-igs. 1'and 3, the molding: apparatus comprises a plurality of superimposed mold plates '10, which are supll having a hollowbylihdrical In either case a greater efiicient manner of applying a mold plate; and

iii)

outlet within and near the top post l2 secured thereto and extending through the peripheries l3-of circular openings It in the mold plates. The mold plates H) are removable from the post i2 and the peripheries |3 of the opening therein have a slidable fit on the post. Mold cavities l5 are formed between the adjacent plates H) for the receptionofplastic material 16, such as vulcanizable rubber compounds, which is molded and set in the form of rings, or grommets. As shown in the drawings, circular recesses i! are formed on each side of the mold plates it. The recesses I? extend radially outwardly from the periphery l3 of the openings M in the plates to form one-half of the mold cavity !5 between the adjacent plates l0.

In molding grommets IS on sheet material 20 around opening 2! therein, as shown in the finished form in Fig. 4,- the plastic lBis placed inthe mold cavity P5 in two parts, comprising rings 22. as shown in Fig. 2, which are placed on each side of the sheet material 20, which latter extends beyond the rings 22 adjacent elevated rims 23 of the mold plates l0.

The superimposed mold plates 10 are clamped together under pressure by a capstan 24, which is threaded onto a stem 25 secured to the post i2.- The capstan 24' is manually operated by handles 25. A ball ring thrust bearing 2'! is interposed between thecapstan 24 and a pressure to be molded, her, or hollow cylindrical post I 2 is heated to H5 in the mold cure; or thermoset the plastic cavities 15. The inner member 12 is heated, as shown in Fig. 1, by admitting a heating fluid, preferably steam, to the-interior of the post H from a pipe 3-3 which is connected to a source of supply. The steam is turned on or oil at the will of the operator by a valve 34, which is adapted to connect the pipe 33 to a pipe 35 having'an of the hollow post I2. The condensate from the steam is drained from the interior of the post I2 through a pipetfi which is connected to the bottom of the interior of the post l2. The drainage from the post I? iscontrolledfby valve 3 'l.

In the practice of the methodfof' applying 20, the openings preferably are so cut that their and is clamped between the v the opening in the fabric 20 and through the axis of the grommet I9, as shown in Fig. 4. The margins of the sheet fabric around the openings 2| to be covered by the grommets are coated with layers 39 of adhesive compatible with the moldable plastic material I6 of which the grommets I5 are made, for the purpose of producing a good bond between the plastic I6 and the fabric 20. The plastic rings 22, as shown in Fig. 2 are preferably cut out of calendered sheet stock, such as a vulcanizable rubber compound. The molding apparatus is then loaded with the uncured plastic rings 22 and the fabric 2 I, as illustrated in Fi 1.

At the beginning of the loading operation, the capstan 24 and pressure ring 28 assembly, and the mold plates I0, excepting the bottom plate, are removed from the post I2. A plastic ring 22 is placed in the recess II of the bottom mold plate IS. The bottom piece of fabric 20 is then placed over the ring 22 and the plate It by passing the opening 2i therein over the top of the post I2. A second plastic ring 22 is then placed over the post I2 and on top of the fabric 20, so as to cover the margin 39 around the opening 2I in the fabric. A second plate It is then placed over the post I2 and on top of the fabric 2I. Successive layers of rings 22 and fabric 2| sandwiched therebetween, and mold plates iii are superimposed upon each other around the post I2, so as to form the successive grommets I9 around the openings in the fabric. After a sufficient number of mold cavities I5 have thus been formed and filled, the capstan 24 is threaded on to the stem 25 at the top of the inner post I2, and pressure is applied to the mold plates I between the pressure ring 28 and the base plate II by turning the capstan down on the stem 25. In so doing the outer periphery of the mold cavity I is sealed by the pressure exerted between the elevated outer peripheral faces 23 of the mold plates II! as a result of the pressure exerted on the plates axially of the openings I3 therein, or perpendicular to the faces of the plates. The fabric extending between the elevated faces 23 of the mold plates I0 acts as a gasket, and thereby assists in the formation of a seal to prevent flash from being extruded. between the plates ID at the outer peripheries of the mold cavities The interior of the post I2 is then heated by admitting steam to the interior thereof through the pipe 35. As the interior of the cylindrical cavity in the post I2 is heated, the outer surface of the post expands more than the periphery of the opening I3 in the plates Ill. It is desirable that the clearance between the post I2 and the inner peripheries I3 of the plates when cold be sufficiently small to form a seal on the inner periphery of the mold cavities, and thereby prevent flash from extruding between the plates I0 and the post I2. During the heating of the moldable material I6, further pressure is exerted on the plates I8 by turning down the capstan 24 on the stem of the post I2. The heat is conducted from the walls of the ost I2 directly to the plastic I6 making contact therewith, and indirectly to the plastic through the mold plates III which make contact with the outer periphery of the post I2. The plastic I6 is heated for a sufficient period of time to thermoset or cure it to the desired degree. During the curing cycle the plastic becomes softened and flows under the pressure of the capstan 24 around the peripheries of the openings 2| in the fabric 20 so as to provide a continuous wall 38 of plastic for the axial opening in each grommet. The softened plastic under the pressure of the capstan is bonded to the fabric 2| with the aid of the adhesive coating 39, which was previously applied around the margin of the opening in the fabric to be covered by the plastic I6 forming the grommet I9. At the end of the curing cycle the steam supply is cut off by closing the valve 34.

In order to cool the mold plates I0, and thereby facilitate their removal from the post I2, and handling at a reduced temperature at the end of the curing cycle, cooling water is admitted to the interior of the post I2. The cooling water is supplied from a pipe 40 by opening a valve H which connects the pipe 40 to the inlet pipe 35 opening into the interior of the post I2. The condensate control valve 36, is opened so as to permit the discharge of the cooling water from the interior of the post I2 at the desired rate.

During the cooling cycle the capstan assembly 24 with the pressure ring 28 may be removed from the post I2, and after the post I2 has been cooled sufliciently to cause the contraction thereof in the event it has been tightly expanded against the inner peripheries I3 of the plates, the superimposed mold plates IO and fabrics 23 with the grommets I9 thereon are removed from around the posts. The superimposed layers of fabric 20 droop downwardly over the outer peripheries of the mold plates and insulate the mold plates from the outside atmosphere, and thereby retain the heat in the mold cavities I5, which is supplied from the interior of the post I2. If the fabric 20 is omitted and rings are being molded, the heat may be retained in the mold cavities by an insulating bag (not shown) which may be placed (Inger the capstan 24 and around the mold plates This apparatus is particularly advantageous in molding grommets on fabric because the heat is supplied to the mold cavities from the interior of the ring shaped mold plates and it is difiicult to transmit the heat to the cavities from the outside thereof through the insulating layers of fabric. Furthermore, where heat is supplied from the exterior the direct application of the heat or steam to the fabric 20 in some cases discolors or shrinks it.

Whereas, the mold disclosed in the drawings has a ring shaped mold cavity, which extends to the periphery I3 of the opening I4 in the mold plate III, and is closed at its inner periphery by the post I2, the mold cavity may encircle the opening and lie wholly within the face of the mold plates as shown in United States Patent No. 2,148,079. The periphery of such mold cavity may be of any shape and have any desired number of sides.

Whereas, the preferred form of the method and apparatus has been described more or less in detail herein, it will be understood that changes may be made in this invention as described without departing from the spirit of the invention, and the scope of the appended claims.

Having thus described our invention, what we claim and desire to protect by Letters Patent is:

l. A molding apparatus comprising a hollow post, a plurality of superimposed mold plates, each of said plates including an end plate having a central opening adapted to fit over and in slidable contact with said post, said plates and posts forming the walls of mold cavities surrounding said post and interposed between said plates, means for applying pressure to the face of said end plate and thereby force said plates towards each other, and means for admitting and exhausting heating fluid to and from said hollow post to conduct heat to said mold cavities.

2. A molding apparatus comprising a base, a plurality of superimposed mold plates supported on said base and having openings therein, a recessed margin extending outwardly from and around said openings in said plates and within the inner periphery of elevated sealing rims thereon so as to form a mold cavity between adjacent faces of said plates, a common post extending through said openings in said plates, means for alternately heating and cooling said post, the peripheries of said opening in said plates having slidable fits on said post when it is cooled and a tight fit when heated, and means for clamping said plates together on said base.

3. A molding apparatus comprising a base, a plurality of superimposed mold plates supported on said base and having openings therein, a hollow post extending through said openings, means for alternately supplying and exhausting a heating and a cooling medium to and from the interior of said post, the peripheries of said openings in said plates having slidable fits on said post after being cooled by said cooling medium 6 and a tight fit after being heated by said heating medium, and means for clamping said plates together on said base.

4. A molding apparatus comprising a base, a plurality of superimposed mold plates supported on said base free from any surrounding structure and having openings therein, a hollow post secured to said base and extending through said openings, a removable capstan on said post for clamping said plates together on said base, means for alternately supplying and exhausting a heating and a cooling medium to and from the interior of said post, the peripheries of said openings having a slidable fit on said post after being cooled by said cooling medium and a tight fit after being heated by said heating medium, each of said plates having a recessed margin extending outwardly from and around said opening therein and within an elevated sealing rim thereon so as to form a mold cavity between adjacent plates.

ELMER VAN RIPER. GEORGE W. FREY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,396,158 Bonner Nov. 8, 1921 2,253,792 Leavenworth Aug. 26, 1941 2,389,178 Blount et al Nov. 20, 1945 2,569,308 Garbin Sept. 25, 1951 

